1. Field of the Invention
The present invention relates to a method of evaluating restitution characteristics of a golf club head which evaluates restitution characteristics of a striking face of the golf club head when a golf ball is struck by the golf club head such as a hollow golf club head made of metal or the like, and relates to a system for evaluating the restitution characteristic, and a golf club.
2. Description of the Related Art
Recently, through improvement and development of structures and materials of golf club heads, golf club manufacturers have proposed a variety of golf clubs having a golf club head with high restitution characteristics so that even a golfer who with weak power may hit a golf ball far.
On the other hand, the United States Golf Association (USGA) promulgates a rule for regulating the golf club that may hit the golf ball too far due to the excessively high restitution characteristics in a professional golf tournament of professional golfers, and stipulates that the golf club with a coefficient of restitution e, obtained by the following method below, of 0.830 or less should be used in the professional golf tournament. According to this, the coefficient of restitution e between the golf ball and the golf club head is given as follows. Under the condition that the golf club head H is laid on a base table, the golf ball is caused to impact perpendicularly to a face F of the golf club head H as shown in FIG. 8, and the coefficient of restitution e is obtained from the formula (indicated below) among an incoming velocity Vin and an outgoing velocity Vout of the golf ball, a mass M of the golf club head and a mass m of the golf ball at this time.Vout/Vin=(e·M−m)/(M+m)
However, when the coefficient of restitution e is calculated according to the above-described method, it is necessary to set the face F of the golf club head H perpendicular to an incoming direction of the golf ball and, in addition, to accurately align the golf club head H for the golf ball to strike the face F at a predetermined striking position. Also, since it is necessary to measure only with the golf club head by removing the golf club head away from the shaft, it is also necessary to perform troublesome work for disassembling the golf club and reassembling the golf club after measurement. Thus, it is almost impossible to examine the golf clubs, one by one, of the professional golfers who participate the tournament within limited time before a start of the tournament for calculating the coefficient of restitution e according to the above-described method.
Also, if the disassembled golf club is reassembled, a favorable impression which the golf club has given to the professional golfer for a long time is often changed.